The present invention relates to a painting method, and more particularly to a method of coating a vertical surface of an object to be painted by ejecting paint sprays from paint spraying means while moving the paint spraying means upwardly from a position near a lower end of the vertical surface of the object to prevent ejected excessive paint from being applied to the paint spraying means.
Automobile industry in recent years employs highly automated line production processes for efficiently mass-producing automobile products. There are used assembling apparatus for assembling individual parts and conveyor apparatus for conveying components to respective working positions. Painting apparatus for painting or coating automobile bodies are also automatized. For example, Japanese Laid-Open Patent Publication No. 63-88081 discloses a technical concept for automatically coating an automotive body.
In the above conventional painting process, an automotive body and paint spraying means are displaced relatively to each other to keep the paint spraying means spaced a constant distance from front, upper, and rear surfaces of the automotive body while ejecting paint from the pain spraying means to coat the front, upper, and rear surfaces sequentially in the order named.
When applying a paint coat to the rear surface of the automotive body, the paint spraying means is lowered while ejecting the paint. Therefore, a paint mist floating in the coating room tends to be applied to the paint spraying means. More specifically, some of the paint ejected from the paint spraying means is not applied to the surface of the automotive body, but remains floating in the coating room. Usually, a downward air stream is forcibly passed through the coating room to cause the paint mist to fall so that no excessive paint coat will be applied to the paint spraying means.
While the paint spraying means and the automotive body are being relatively displaced at a predetermined speed, the speed of downward movement of the paint spraying means for coating the rear surface of the automotive body is higher than the speed at which the paint mist drops, because it is necessary to move the paint spraying means at a relatively high speed for efficiently coating the automotive body. When paint is ejected from the paint spraying means that is descending along the rear surface of the automotive body, excessive paint which falls as a slow mist below the paint spraying means tends to be attached to the paint spraying means. If the paint spraying means with such paint mist deposits carried thereon were continuously used, the paint mist deposits would drop onto the coated surface of the automotive body, thus deteriorating the coated layer on the automotive body. To avoid this, the paint spraying means has to be cleaned frequently. The cleaning process is tedious and time-consuming, and makes the entire coating procedure less efficient.